Research Focus: Two-Fluid Plasma Physics

A plasma is a gas that is significantly ionized and thus is composed of electrons and ions. Plasmas are usually permeated by electromagnetic (EM) fields. In addition to long range smoothed or averaged EM fields there are localized short range micro-fields on individual particles. The long range fields act like body forces while the short range fields like collisions. The micro-fields are responsible for the transmission of pressure and viscous forces, for the conduction of particle energy, and for diffusion between components of the plasma. The dynamical behavior of plasmas is strongly dependent on frequency. At the lowest frequency the motion of the electrons and ions are locked together by electrostatic forces and the plasma behaves like an electrically conducting fluid. This is the regime of magnetohydrodynamics (MHD). At somewhat higher frequencies the electrons and ions can move relative to each other, behaving like two separate, interpenetrating fluids. This Two-Fluid regime is currently the primary focus of my research. At still higher frequencies the distribution function of the plasma species is driven by anisotropies in the velocity space. This regime is best described by the collisionless Boltzmann equation or Vlasov equation of kinetic theory.

My current research focuses on developing efficient methods for the solution of the Two-Fluid equations. This model is described by a set of 18 partial differential equations: 5 Euler equations for each fluid and 8 Maxwell's equations. We have successfully applied this model to understanding collisionless magnetic reconnection and axisymmetric Z-pinches. We have also made some progress in understanding stability of Field Reverse Configuration (FRC). FRCs are compact devices being actively investigated for fusion power generation and electric thrusters.